Marathon runners know that they can “hit the wall” or “bonk” in a long race. The “Bonk” as we call it normally happens when either our muscles or the brain runs out of energy. But sometimes the bonk comes hard and early in a race. If by mile four or five, you’re out of gas then something else is amiss. Today I handle one of my athlete’s questions to illustrate what kinds of factors can cause the early or “Pre-mature Bonk”. First, the question:

“My half marathon yesterday sucked. I finished in 2:07 and I was going for a PR of 1:58. I had to stop and walk a few times. Then I would get bursts of energy just like you described. . . .But I was completely tanked. I didn’t have any digestive problems at all, just a total lack of energy. . . .I felt so depleted. I finally pushed through at the “1/4 mile to go!” marker but nearly dropped after stepping on the finish mat. Oh, and did I tell you it was 85 degrees yesterday?”

Post-race Fatigue at WMA 2011

There’s a couple of things that I want you to think about here in regards to why you might have bonked so hard and early in your race, keeping in mind here that we’re talking about a half-marathon so your bonk comes even earlier than your longest workouts. Here are three things that I want you to focus on:

First, is the impact of your training itself on your energy level. The fatigue you’re describing can be a symptom of what you’re doing in your workouts leading up to the race. The amount of recovery (or lack of recovery) is a big factor in how you feel during any particular workout. So if you think about your muscles as having a fuel tank, those tanks may not be getting refilled after your workouts and leading up to the half-marathon. One of the key differences between an “A” race and all the others (meaning one that you’re really training for rather than one that is just on the schedule along the way) is the taper period that comes before the race. This is a period of weeks that comes right before the race in which the body gets a chance to fully recover. What you’re describing below sounds typical of what happens when you run a race without a taper (or rather without recovery from your workouts right before it.) This isn’t actually a bad thing. It puts a level of stress on the body that ends up being helpful to your training in the long run, but it doesn’t feel great.

This tends to be the case when you are training at longer distances (e.g. 15-20 miles) and the fatigue hits early, perhaps as early as 2-3 miles. In these cases, the fatigue is likely a symptom of a the hard effort of your training. The good news is that when you’ve given yourself some recovery in your taper then this won’t be a problem in a more important “A” race.

Second, in terms of fuel you need to constantly be in the process of preparing for the next workout. The big question here is what you’re eating on a daily basis. Runners need to be replacing energy as soon as workouts end and making sure that they are eating for recovery to prepare for the next workout, which may come as little as a day or a few hours after the previous one. You want to make sure that you’re eating a well balanced diet every day. Another way to put this is that you don’t prepare for a big workout or race in one meal, but rather in all of your meals.

Also, you may want to ensure that you’re getting enough vitamins in your diet. You can really combat a lack of daily energy with a good daily multi-vitamin and a B complex. B vitamins are really important for energy. Getting enough nutrients in your diet does a lot to help with energy levels. A product that I would recommend is the Vega Whole Food Optimizer. This is a smoothie-base that you can mix with fruit, juice or water and have for breakfast. It is a complete meal and includes all of the proteins, vitamins and minerals that you need. It isn’t cheap. It’s available on-line and at food retailers like Whole Foods. I suggest using a product like this in the morning to give you a strong nutritional base for the entire day.

Finally, the temperature and other weather conditions are certainly factors in your performance and can manifest themselves as fatigue. Running in heat and humidity is best thought of like running up a steep hill. It dramatically increases the effort level, even at the same pace. So if you were trying to run the same pace at 85 degrees that you normally run at 65 degrees, it is going to feel much, much harder. I’d normally advise people to back off the pace by about 10% per 10 degrees of temperature increase over their typical training temperature.

Hydration plays a big role, but so long as you were drinking plenty of fluids you were probably doing what you could to combat the dehydration. Similar to eating, hydration doesn’t happen overnight. Make sure that you’re drinking 2-3 liters of clear fluid (meaning water) every day to keep well hydrated. Leaving it to the last minute is kind of like pouring water on a dry sponge. Most of the water rolls off. A wet sponge actually absorbs more water than a dry one. Think of your muscles in that same way. And keep in mind that alcohol works in the opposite direction and has a net dehydrating effect. It’s best not to drink alcohol at all within 2-3 days of any major race or long workout.

The bottom line is that factors such as the volume and intensity of your training, your diet and recovery, and external factors such as weather are often responsible when the bonk comes early and hard. Understand that if you’ve been training a specific pace and you experience this early in a race, one or more of these factors are probably in play.